Multiphase controller communication

ABSTRACT

A multiphase controller includes an integrator enable terminal, a pulse width modulator, an error integrator, an open drain driver, and an integrator enable circuit. The integrator enable terminal is adapted to be coupled to the integrator enable terminal of a different instance of the multiphase controller. The pulse width modulator is configured to modulate a power stage. The error integrator is configured to control the pulse width modulator. The open drain driver is coupled to the integrator enable circuit. The integrator enable circuit is coupled to the pulse width modulator, the error integrator, the open drain driver, and the integrator enable terminal. The integrator enable circuit is configured to activate the open drain driver responsive to generation of a power stage control pulse by the pulse width modulator, and activate the error integrator responsive to a logic low signal at the integrator enable terminal.

BACKGROUND

As systems and integrated circuits (e.g., processors, applicationspecific integrated circuits, etc.) become more complex, the powerrequirements of these circuits also become more complex. Multiphaseregulators are increasingly used to provide power to such systems andcircuits. A multiphase regulator includes multiple (e.g., 2-12) parallelpower stages each including power transistors and an inductor. Amultiphase controller coordinates the switching of the power stages. Themultiphase controller activates the power stages at spaced intervals toproduce a desired output voltage.

SUMMARY

In one example, a multiphase controller includes an integrator enableterminal, a pulse width modulator, an error integrator, an open draindriver, and an integrator enable circuit. The error integrator iscoupled to the pulse width modulator, and includes an enable inputcoupled to the integrator enable terminal. The open drain driverincludes a current terminal and a control terminal. The current terminalis coupled to the integrator enable terminal. The integrator enablecircuit includes an input coupled to the pulse width modulator, and anoutput coupled to the control terminal of the open drain driver.

In another example, a multiphase controller includes an integratorenable terminal, a pulse width modulator, an error integrator, an opendrain driver, and an integrator enable circuit. The integrator enableterminal is adapted to be coupled to the integrator enable terminal of adifferent instance of the multiphase controller. The pulse widthmodulator is configured to modulate a power stage. The error integratoris configured to control the pulse width modulator. The open draindriver is coupled to the integrator enable circuit. The integratorenable circuit is coupled to the pulse width modulator, the errorintegrator, the open drain driver, and the integrator enable terminal.The integrator enable circuit is configured to activate the open draindriver responsive to generation of a power stage control pulse by thepulse width modulator, and activate the error integrator responsive to alogic low signal at the integrator enable terminal.

In a further example, a multiphase converter includes a first multiphasecontroller, a second multiphase controller, and a power stage. The firstmultiphase controller includes an integrator enable terminal, and acontroller startup terminal. The power stage includes a temperaturesense terminal coupled to the control startup terminal of the firstmultiphase controller. The second multiphase controller includes acontroller startup terminal, an integrator, a pulse width modulator, anerror integrator, an open drain driver, and an integrator enablecircuit. The controller startup terminal of the second multiphasecontroller is coupled to the temperature sense terminal of the powerstage. The integrator enable terminal of the second multiphasecontroller is coupled to the integrator enable terminal of the firstmultiphase controller. The pulse width modulator is configured tomodulate the power stage. The error integrator is configured to controlthe pulse width modulator. The open drain driver is coupled to theintegrator enable terminal of the second multiphase controller. Theintegrator enable circuit is coupled to the pulse width modulator, theerror integrator, the open drain driver, and the integrator enableterminal of the second multiphase controller. The integrator enablecircuit is configured to activate the open drain driver responsive togeneration of a power stage control pulse by the pulse width modulator,and activate the error integrator responsive to the first multiphasecontroller generating a logic low signal at the integrator enableterminal of the second multiphase controller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram for an example multistage DC-DC converter thatincludes stacked multiphase controllers with inter-controllercommunication.

FIG. 2 is a block diagram for example startup synchronization circuitryincluded in the stacked multiphase controllers of FIG. 1 .

FIG. 3 is flow diagram for an example method for startup synchronizationof stacked multiphase controllers.

FIG. 4 is a block diagram for example integrator startup circuitryincluded in the stacked multiphase controllers of FIG. 1 .

FIG. 5 shows an example of signals in the integrator startup circuitryof FIG. 4 .

FIG. 6 is a block diagram for example fault communication circuitryincluded in the stacked multiphase controllers of FIG. 1 .

FIG. 7 is a flow diagram for an example method for fault communicationin stacked multiphase controllers.

DETAILED DESCRIPTION

As the current demands of modern circuits increase, the number of powerstages (phases) needed in a multiphase regulator to meet the currentdemand also increases. Each power stage is controlled via at least twopins of a multiphase controller. Thus, the multiphase controller pincount increases with the number of power stages. To enable control ofthe increasing number of power stages, multiphase controllers may becoupled in parallel (stacked) to the power stages. Each of the stackedmultiphase controllers supports N power stages, and K stackedcontrollers support K*N power stages. In some systems, one of thestacked controllers serves as the primary controller, and the remainderof the stacked controllers serve as secondary controllers.

When using stacked multiphase controllers, the operation of thecontrollers should be coordinated to properly control the power stages.To simulate the operation of a single controller, the stackedcontrollers should start and stop together. Differences in clockfrequency and initialization time of various analog blocks of thecontrollers can cause different controllers to start-up at differenttimes. Controller start-up and shut-down should be managed to ensurethat the various power supplies supported by the controllers are startedand stopped in the proper order. Uncontrolled shutdown of the stackedmultiphase controllers may result in system operational errors or damageif the power supplies associated with the controllers shut-down out ofsequence.

The multiphase controllers described herein allow communication ofstartup enable signals, control loop enable signals, and fault signalsbetween any number of stacked multiphase controllers without increasingthe number of pins provided in the controller packaging. To controlstartup timing, each multiphase controller drives a startup enablesignal using an open-drain output coupled to a package pin used receivepower stage ready status. All of the stacked multiphase controllersstartup when all of the stacked multiphase controllers are ready.

The package pin used to communicate the startup enable signal may alsobe used to communicate a fault signal to all of the stacked multiphasecontrollers. Each multiphase controller drives a fault signal using anopen-drain output coupled to a package pin. When any multiphasecontroller detects a fault, the controller drives the fault signal, andall of the controllers shut down.

Each of the multiphase controllers includes an error integrator tocontrol output voltage and/or current. Each error integrator is enabledresponsive to pulse width modulation. To coordinate operation of theerror integrators, each multiphase controller drives an enable signalusing an open-drain output coupled to a package I/O pin. The first ofthe stacked multiphase controllers to generate a pulse-width modulatorpulse drives the enable signal to enable the error integrators of all ofthe stacked multiphase controllers.

FIG. 1 is a block diagram for an example multistage DC-DC converter 100that includes stacked multiphase controllers with inter-controllercommunication. The multistage DC-DC converter 100 includes a multiphasecontroller 102, a multiphase controller 104, a power stage 106, a powerstage 108, a power stage 110, and a power stage 112. The multiphasecontroller 102 may be similar or identical to the multiphase controller104. The power stage 106, power stage 108, power stage 110, and powerstage 112 may be similar or identical to one another. The power stage106 and the power stage 108 are coupled to the multiphase controller102. The power stage 110 and the power stage 112 are coupled to themultiphase controller 104. In practice, the multistage DC-DC converter100 may include 2 or more multiphase controllers, and two or more powerstages may be coupled to each of the multiphase controllers. Eachmultiphase controller controls switching of the power transistorsprovided in the power stages coupled to the multiphase controller tocharge an inductor coupled to each power stage. For example, themultiphase controller 102 controls switching of the power stage 106 tocharge the inductor 114, and controls switching of the power stage 108to charge the inductor 116. Similarly, the multiphase controller 104controls switching of the power stage 110 to charge the inductor 118,and controls switching of the power stage 112 to charge the inductor120. A load circuit, such as the processor 122, is coupled to theinductors.

Pulse width modulation outputs 102A and 102B of the multiphasecontroller 102 are respectively coupled to pulse width modulationcontrol inputs 106A and 108A of the power stage 106 and the power stage108 to control switching of the power stage 106 and the power stage 108.Similarly, pulse width modulation outputs 104A and 104B of themultiphase controller 104 are respectively coupled to pulse widthmodulation control inputs 110A and 112A of the power stage 110 and thepower stage 112 to control switching of the power stage 110 and thepower stage 112.

The multiphase controller 102 and the multiphase controller 104 includeinter-controller communication circuitry 124 that enables communicationof synchronization information between the multiphase controller 102 andthe multiphase controller 104. To reduce the number of package pinsneeded to provide communication between the multiphase controller 102and the multiphase controller 104, communication is provided usingpackage pins assigned to other functions. The synchronization functionsprovided by the inter-controller communication circuitry 124 includestartup, integrator, and shutdown synchronization. The controllerstartup terminal 102C of the multiphase controller 102 is coupled to thecontroller startup terminal 104C of the multiphase controller 104 toprovide multiphase controller startup synchronization. The temperaturestatus terminal 106B of the power stage 106, the temperature statusterminal 108B of the power stage 108, the temperature status terminal1108 of the power stage 110, and the temperature status terminal 112B ofthe power stage 112 are also coupled to the controller startup terminal102C and the controller startup terminal 104C for communication oftemperature information from the power stages to the multiphasecontrollers. Thus, communication of controller startup synchronizationinformation is provided via package pins that are also used to receivetemperature information from the power stages.

The integrator enable terminal 102D of the multiphase controller 102 iscoupled to the integrator enable terminal 104D of the multiphasecontroller 104 for communication of integrator synchronizationinformation between the multiphase controller 102 and the multiphasecontroller 104.

Fault information is communicated between the multiphase controller 102and the multiphase controller 104 via the controller startup terminal102C and the controller startup terminal 104C (the controller startupterminal 102C and the controller startup terminal 104C may also bereferred to as controller fault terminals). Thus, fault information iscommunicated via package pins that are also used to communicatecontroller startup synchronization information and power stagetemperature information. The average current terminal 102E is coupled tothe average current terminal 104E for communication of average currentinformation between the multiphase controller 102 and the multiphasecontroller 104. The average current terminal 102E and the averagecurrent terminal 104E are also used to communicate additional faultinformation between the multiphase controller 102 and the multiphasecontroller 104. Thus, fault information is shared via package pins thatare also used to share average current information.

FIG. 2 is a block diagram of example startup synchronization circuitry200. The startup synchronization circuitry 200 may be included in theinter-controller communication circuitry 124 of the multiphasecontroller 102 and the multiphase controller 104. The startupsynchronization circuitry 200 includes an open drain driver 202, acontroller enable circuit 204, a comparator 206, and a voltage referencecircuit 208. The open drain driver 202 is an N-type field effecttransistor (FET) having a first current terminal (drain) coupled to thecontroller startup terminal 102C, and a second current terminal (source)coupled to ground. A control terminal (gate) of the open drain driver202 is coupled to the controller enable circuit 204. A first input ofthe comparator 206 is coupled to the controller startup terminal 102C,and a second input of the comparator 206 is coupled to the voltagereference circuit 208. An output of the comparator 206 is coupled to thecontroller enable circuit 204.

Operation of the startup synchronization circuitry 200 is explained byreference to the multiphase controller 102. The multiphase controller104 operates in similar fashion. At initialization of the multiphasecontroller 102, the controller enable circuit 204 activates the opendrain driver 202 to pull down the voltage at the controller startupterminal 102C. When the multiphase controller 102 is ready to start up(power supply voltages reach operational levels, firmware has executedto a startup point, operation is enabled via externally generated signalor firmware, etc.), the controller enable circuit 204 deactivates theopen drain driver 202. When the open drain drivers 202 of the multiphasecontroller 102 and the multiphase controller 104 are deactivated, thevoltage at the controller startup terminal 102C goes high. Thecomparator 206 compares the voltage at the controller startup terminal102C to a threshold provided by the voltage reference circuit 208. Thethreshold voltage provided by the voltage reference circuit 208 may beabout 280 millivolts in some implementations of the startupsynchronization circuitry 200. When the voltage at the controllerstartup terminal 102C exceeds the threshold, the output of thecomparator 206 goes high to notify the controller enable circuit 204that all multiphase controllers of the multistage DC-DC converter 100are ready to start up, and the controller enable circuit 204 triggersthe multiphase controller 102 to start up (e.g., start modulation of thepower stages). Thus, the startup synchronization circuitry 200synchronizes startup of the multiphase controller 102 and the multiphasecontroller 104 to avoid issues caused by different initialization timesfor various circuits (analog circuits, firmware timing, etc.) of thedifferent multiphase controllers.

FIG. 2 also shows an analog-to-digital converter 210 coupled to thecontroller startup terminal 102C for digitizing temperature informationreceived from the power stages.

FIG. 3 is flow diagram for an example method 300 for startupsynchronization of stacked multiphase controllers 102 and 104. Thoughdepicted sequentially as a matter of convenience, at least some of theactions shown can be performed in a different order and/or performed inparallel. Additionally, some implementations may perform only some ofthe actions shown. Operations of the method 300 are explained withreference to the multiphase controller 102. The multiphase controller104 also executes the method 300.

In block 302, power is provided to the multiphase controller 102. Thepower may include a first voltage to power analog circuits and a secondvoltage to power digital circuits.

In block 304, the controller enable circuit 204 activates the open draindriver 202 to pull down the voltage at the controller startup terminal102C. The controller enable circuit 204 may activate (turn on) the opendrain driver 202 as soon as possible after power is applied to themultiphase controller 102 in block 302.

In block 306, an input voltage (Vin) provided to the multiphasecontroller 102 is compared to an input voltage threshold (Vin_on). Whenthe input voltage exceeds the input voltage threshold, in block 308, thecontroller enable circuit 204 deactivates the open drain driver 202 toindicate that the multiphase controller 102 is ready to start up (e.g.,ready to begin modulation of the power stage 106 and the power stage108. Embodiments of the method 300 may check the state of variousoperating parameters of the multiphase controller 102 in block 306 todetermine whether the multiphase controller 102 is ready to start up.

In block 310, the comparator 206 compares the voltage at the controllerstartup terminal 102C to a threshold voltage. The voltage at themultiphase controller 102 will exceed the threshold voltage when boththe multiphase controller 102 and the multiphase controller 104 havedeactivated the open drain driver 202 in block 306. When the voltage atthe multiphase controller 102 exceeds the threshold voltage, themultiphase controller 102 starts up in block 312. Thus, only after bothof the multiphase controller 102 and the multiphase controller 104indicate ready, do either start up.

FIG. 4 is a block diagram for example integrator startup circuitry 400.A portion of the integrator startup circuitry 400 may be included in theinter-controller communication circuitry 124 of the multiphasecontroller 102 and the multiphase controller 104. The integrator startupcircuitry 400 includes an error integrator 402, a pulse width modulator404, an open drain driver 408, an integrator enable circuit 410, and aninverter 412. The open drain driver 408, the integrator enable circuit410, and the inverter 412 may be included in the inter-controllercommunication circuitry 124 of the multiphase controller 102 and themultiphase controller 104. The open drain driver 408 is an N-type fieldeffect transistor (FET) having a current terminal (drain) coupled to theintegrator enable terminal 102D and a current terminal (source) coupledto ground. A control terminal (gate) of the open drain driver 408 iscoupled to the integrator enable circuit 410. Operation of theintegrator startup circuitry 400 is explained by reference to themultiphase controller 102. The multiphase controller 104 operates insimilar fashion.

The error integrator 402 and the pulse width modulator 404 arecomponents of the regulator control loop of the multiphase controller102 and the power stages coupled to the multiphase controller 102. Theerror integrator 402 integrates an error signal that defines adifference of a reference signal and a feedback signal in the multiphasecontroller 102. The reference signal may be representative of a targetoutput voltage, or may be representative of current output of theprimary multiphase controller (e.g., the multiphase controller 102). Thefeedback signal may be representative of the output voltage of themultistage DC-DC converter 100, or may be representative of the outputcurrent of the secondary multiphase controller (e.g., the multiphasecontroller 104). The integrated error signal generated by the errorintegrator 402 is provided to the pulse width modulator 404 forcontrolling the pulse width modulator 404. The pulse width modulator 404generates pulses (power stage control pulses) for regulating the outputvoltage of the multistage DC-DC converter 100. The power stage pulsecircuitry 406 is coupled to the pulse width modulator 404, and providesPWM pulses to the power stages coupled to the multiphase controller 102.

The integrator enable circuit 410 controls activation of the errorintegrator 402 to ensure that the multiphase controller 102 andmultiphase controller 104 start modulation of the power stages at aboutthe same time. An output 410A of the integrator enable circuit 410 iscoupled to an input 402A of the error integrator 402 for communicationof an integrator enable signal. An input 410B of the integrator enablecircuit 410 is coupled to the pulse width modulator 404 for receipt of aPWM output pulse. When the multiphase controller 102 is initializing (atpower up), the error integrator 402 is disabled, and the integratorenable circuit 410 deactivates the open drain driver 408 to allow thevoltage at the integrator enable terminal 102D to rise. When the pulsewidth modulator 404 generates an output pulse, the integrator enablecircuit 410 activates the open drain driver 408 to pull down the voltageat the integrator enable terminal 102D. The integrator enable circuit410 monitors the voltage at the integrator enable terminal 102D, via theinverter 412. When the voltage at the integrator enable terminal 102D ispulled down, by the open drain driver 408 of the multiphase controller102 or the multiphase controller 104, the integrator enable circuit 410enables the error integrator 402, via an enable signal provided at theoutput 410A. Thus, when either the multiphase controller 102 or themultiphase controller 104 generates a PWM pulse, the error integratorsin both the multiphase controller 102 and the multiphase controller 104are enabled to regulate the output voltage of the multistage DC-DCconverter 100.

FIG. 5 shows an example of signals in the integrator startup circuitry400. When the pulse width modulator 404 of the multiphase controller 102generates the PWM pulse 502, the integrator enable circuit 410 activatesthe driver control signal 503 (DRIVER CONTROL) to turn on the open draindriver 408 and pull the voltage 504 (INTG_CTRL) at the integrator enableterminal 102D low. The integrator enable circuit 410 of the multiphasecontroller 102 and the multiphase controller 104 detect the voltage 504low, and activate the integrator enable signal 506 (INTG_EN) to enablethe error integrators 402 in the multiphase controller 102 and themultiphase controller 104. With its error integrator 402 enabled, themultiphase controller 404 generates the PWM pulse 508.

FIG. 6 is a block diagram for an example fault communication circuit600. The fault communication circuit 600 may be included in theinter-controller communication circuitry 124 of the multiphasecontroller 102 and the multiphase controller 104. The faultcommunication circuit 600 includes a fault circuit 602, an open draindriver 604, an open drain driver 606, a comparator 608, a comparator612, a voltage reference circuit 610, and a voltage reference circuit614. Operation of the fault communication circuit 600 is explained byreference to the multiphase controller 102. The multiphase controller104 operates in similar fashion.

The fault circuit 602 detects faults (e.g., overvoltage, undervoltage,overcurrent, etc.) in the multiphase controller 102, communicates faultinformation to the multiphase controller 104 via the open drain driver604 and the open drain driver 606, and receives fault information fromthe multiphase controller 104 via the comparator 608 and the comparator612. An output 602A of the fault circuit 602 is coupled to the controlterminal (gate) of the open drain driver 604, and an output 602B of thefault circuit 602 is coupled to the control terminal (gate) of the opendrain driver 606. A first current terminal (drain) of the open draindriver 604 is coupled to the controller startup terminal 102C, and asecond current terminal (source) of the open drain driver 604 is coupledto ground. A first current terminal (drain) of the open drain driver 606is coupled to the average current terminal 102E, and a second currentterminal (source) of the open drain driver 604 is coupled to ground. Theopen drain driver 604 and the open drain driver 606 may N-type FETs.

In some implementations of the fault communication circuit 600, the opendrain driver 604 may be implemented using the open drain driver 202 ofthe startup synchronization circuitry 200. That is the open drain driver202 and the open drain driver 604 may be the same transistor. Afterstartup, the signal at the controller startup terminal 102C communicatesfault information. Before startup, the signal at the controller startupterminal 102C communicates controller ready information.

The comparator 612 compares the voltage at the controller startupterminal 102C to a fault threshold voltage provided by the voltagereference circuit 614 to determine whether a fault has been detected bythe multiphase controller 104. The fault threshold voltage provided bythe voltage reference circuit 614 may be about 280 millivolts in someimplementations of the fault communication circuit 600. The output ofthe comparator 612 is coupled to an input 602C of the fault circuit 602for communication of fault information to the fault circuit 602. In someimplementations of the fault communication circuit 600, the voltagereference circuit 614 may be implemented using the comparator 206 of thestartup synchronization circuitry 200. That is the comparator 206 andthe voltage reference circuit 614 may be the same comparator.

Different types of faults trigger different responses in the multiphasecontroller 102 and the multiphase controller 104. For example, somefaults cause the PWM outputs (e.g., PWM outputs 102A, 102B) totransition to a high impedance state (tri-state), while other faults(e.g., overvoltage fault) cause the PWM outputs to be pulled low. Signalprovided at the average current terminal 102E communicates whether thePWM outputs should be tri-stated or pulled low. For example, if thefault circuit 602 detects an overvoltage fault, then, responsive todetection of the overvoltage fault, the fault circuit 602 activates theopen drain driver 604 to indicate that a fault has been detected, andactivates the open drain driver 606 to indicate that the PWM outputsshould be pulled low. If the fault circuit 602 detects fault for whichthe PWM outputs should be tri-stated, the fault circuit 602 activatesthe open drain driver 604 and deactivates the open drain driver 606. Thefault communication circuit 600 of the multiphase controller 104 detectsthe signals transmitted by the multiphase controller 102 at thecontroller startup terminal 104C and the average current terminal 104Eand initiates shutdown.

The comparator 608 compares the voltage at the average current terminal102E to an overvoltage fault threshold voltage provided by the voltagereference circuit 610 to determine what PWM response is indicated. Theovervoltage fault threshold voltage provided by the voltage referencecircuit 610 may be about 280 millivolts in some implementations of thefault communication circuit 600. The output of the comparator 608 iscoupled to an input 602D of the fault circuit 602 for communication offault information to the fault circuit 602.

FIG. 7 is a flow diagram for an example method 700 for faultcommunication in stacked multiphase controllers. Though depictedsequentially as a matter of convenience, at least some of the actionsshown can be performed in a different order and/or performed inparallel. Additionally, some implementations may perform only some ofthe actions shown. Operations of the method 700 are explained withreference to the multiphase controller 102. The multiphase controller104 also executes the method 700.

In block 702, the fault circuit 602 is monitoring operation of themultiphase controller 102 for the presence of faults. If a fault isdetected in block 702, then the fault circuit 602 activates the opendrain driver 604 to pull down the voltage at the controller startupterminal 102C.

In block 706, if the fault detected in block 702 is an overvoltagefault, or other fault that requires pull down of the PWM outputs, thenthe fault circuit 602 activates the open drain driver 606, in block 708,to pull down the voltage at the average current terminal 102E.

In block 710, the multiphase controller 102 and the multiphasecontroller 104 shut down in accordance with fault information providedat the controller startup terminal 102C and the average current terminal102E.

In this description, the term “couple” or “couples” may coverconnections, communications, or signal paths that enable a functionalrelationship consistent with this description. For example, if device Agenerates a signal to control device B to perform an action: (a) in afirst example, device A is coupled to device B; or (b) in a secondexample, device A is coupled to device B through intervening component Cif intervening component C does not substantially alter the functionalrelationship between device A and device B, such that device B iscontrolled by device A via the control signal generated by device A.Also, in this description, the recitation “based on” means “based atleast in part on.” Therefore, if X is based on Y, then X may be afunction of Y and any number of other factors.

Modifications are possible in the described embodiments, and otherembodiments are possible, within the scope of the claims.

What is claimed is:
 1. A multiphase controller, comprising: anintegrator enable terminal; a pulse width modulator; an error integratorcoupled to the pulse width modulator, and including: an enable inputcoupled to the integrator enable terminal; an open drain driverincluding: a current terminal coupled to the integrator enable terminal;and a control terminal; and an integrator enable circuit including: afirst input coupled to the pulse width modulator; a second input coupledto the integrator enable terminal; a first output coupled to the enableinput of the error integrator; and a second output coupled to thecontrol terminal of the open drain driver.
 2. The multiphase controllerof claim 1, wherein: the open drain driver is a first open drain driver;and the multiphase controller further includes: a controller startupterminal; a second open drain driver including: a current terminalcoupled to the controller startup terminal; and a control terminal; anda controller enable circuit coupled to the control terminal of thesecond open drain driver.
 3. The multiphase controller of claim 2,wherein the controller startup terminal is adapted to be coupled to atemperature sense terminal of a power stage.
 4. The multiphasecontroller of claim 1, wherein: the open drain driver is a first opendrain driver; and the multiphase controller further includes: acontroller fault terminal; a second open drain driver including: acurrent terminal coupled to the controller fault terminal; and a controlterminal; and a fault circuit including an output coupled to the controlterminal of the second open drain driver.
 5. The multiphase controllerof claim 4, wherein the controller fault terminal is adapted to becoupled to a temperature sense terminal of a power stage.
 6. Themultiphase controller of claim 4, further comprising: a comparatorincluding: a first input coupled to the controller fault terminal; asecond input coupled to a voltage reference circuit; and an outputcoupled to an input the fault circuit.
 7. The multiphase controller ofclaim 4, further comprising: an average current terminal; and a thirdopen drain driver, including: a current terminal coupled to the averagecurrent terminal; and a control terminal; wherein: the output of thefault circuit is a first output; and the fault circuit includes a secondoutput coupled to the control terminal of the third open drain driver.8. The multiphase controller of claim 7, further comprising: acomparator including: a first input coupled to the average currentterminal; a second input coupled to a voltage reference circuit; and anoutput coupled to an input of the fault circuit.
 9. A multiphasecontroller, comprising: an integrator enable terminal adapted to becoupled to the integrator enable terminal of a different multiphasecontroller; a pulse width modulator configured to modulate a powerstage; an error integrator configured to control the pulse widthmodulator; an open drain driver coupled to the integrator enableterminal; and an integrator enable circuit coupled to the pulse widthmodulator, the error integrator, the open drain driver, and theintegrator enable terminal, and configured to: activate the open draindriver responsive to generation of a power stage control pulse by thepulse width modulator; and activate the error integrator responsive to alogic low signal at the integrator enable terminal.
 10. The multiphasecontroller of claim 9, wherein: the open drain driver is a first opendrain driver; and the multiphase controller further includes: acontroller startup terminal adapted to be coupled to the controllerstartup terminal of the different multiphase controller; a second opendrain driver coupled to the controller startup terminal; and acontroller enable circuit coupled to the second open drain driver, andconfigured to: deactivate the open drain driver responsive to themultiphase controller being ready for operation; and activate the opendrain driver responsive to a start of initialization of the multiphasecontroller.
 11. The multiphase controller of claim 10, wherein thecontroller startup terminal is adapted to be coupled to a temperaturesense terminal of the power stage.
 12. The multiphase controller ofclaim 9, wherein: the open drain driver is a first open drain driver;and the multiphase controller further includes: a controller faultterminal adapted to be coupled to the controller fault terminal of thedifferent multiphase controller; a second open drain driver coupled tothe controller fault terminal; and a fault circuit coupled to the secondopen drain driver, and configured to: activate the second open draindriver responsive to detection of a fault in the multiphase controller.13. The multiphase controller of claim 12, wherein the controller faultterminal is adapted to be coupled to a temperature sense terminal of thepower stage.
 14. The multiphase controller of claim 12, furthercomprising a comparator configured to compare a voltage at thecontroller fault terminal to a fault threshold voltage.
 15. Themultiphase controller of claim 12, further comprising: an averagecurrent terminal adapted to be coupled to the average current terminalof the different multiphase controller; and a third open drain drivercoupled to the average current terminal and the fault circuit; whereinthe fault circuit is configured to activate the third open drain driverresponsive to detection of an overvoltage fault.
 16. The multiphasecontroller of claim 15, further comprising a comparator coupled to theaverage current terminal and the fault circuit, and configured tocompare a voltage at the average current terminal to an overvoltagefault threshold voltage.
 17. A multiphase converter, comprising: a firstmultiphase controller including: an integrator enable terminal; and acontroller startup terminal; a power stage including a temperature senseterminal coupled to the control startup terminal of the first multiphasecontroller; a second multiphase controller including: a controllerstartup terminal coupled to the temperature sense terminal of the powerstage; an integrator enable terminal coupled to the integrator enableterminal of the first multiphase controller; a pulse width modulatorconfigured to modulate the power stage; an error integrator configuredto control the pulse width modulator; an open drain driver coupled tothe integrator enable terminal of the second multiphase controller; andan integrator enable circuit coupled to the pulse width modulator, theerror integrator, the open drain driver, and the integrator enableterminal of the second multiphase controller, and configured to:activate the open drain driver responsive to generation of a power stagecontrol pulse by the pulse width modulator; and activate the errorintegrator responsive to the first multiphase controller generating alogic low signal at the integrator enable terminal of the secondmultiphase controller.
 18. The multiphase converter of claim 17,wherein: the open drain driver of the second multiphase controller is afirst open drain driver; and the second multiphase controller furtherincludes: a second open drain driver coupled to the controller startupterminal of the second multiphase controller; and a controller enablecircuit coupled to the second open drain driver, and configured to:deactivate the second open drain driver responsive to the secondmultiphase controller being ready for operation; and activate the opendrain driver responsive to a start of initialization of the secondmultiphase controller.
 19. The multiphase converter of claim 18,wherein: the second multiphase controller includes: a third open draindriver coupled to the controller startup terminal; and a fault circuitcoupled to the third open drain driver, and configured to: activate thethird open drain driver responsive to detection of a fault in the secondmultiphase controller.
 20. The multiphase converter of claim 19,wherein: the first multiphase controller includes an average currentterminal; and the second multiphase controller includes: an averagecurrent terminal coupled to the average current terminal of the firstmultiphase controller; and a fourth open drain driver coupled to theaverage current terminal of the second multiphase controller and thefault circuit; and the fault circuit is configured to activate thefourth open drain driver responsive to detection of an overvoltagefault.
 21. The multiphase converter of claim 20, wherein the secondmultiphase controller includes a comparator coupled to the averagecurrent terminal and the fault circuit, and configured to compare avoltage at the average current terminal to an overvoltage faultthreshold voltage.
 22. The multiphase converter of claim 17, wherein:the second multiphase controller includes a comparator configured tocompare a voltage at the controller startup terminal to a faultthreshold voltage.